全文获取类型
收费全文 | 180692篇 |
免费 | 21789篇 |
国内免费 | 7654篇 |
专业分类
电工技术 | 15046篇 |
技术理论 | 13篇 |
综合类 | 18360篇 |
化学工业 | 17725篇 |
金属工艺 | 7328篇 |
机械仪表 | 16709篇 |
建筑科学 | 21060篇 |
矿业工程 | 6911篇 |
能源动力 | 8163篇 |
轻工业 | 14921篇 |
水利工程 | 7796篇 |
石油天然气 | 8406篇 |
武器工业 | 2038篇 |
无线电 | 10702篇 |
一般工业技术 | 17806篇 |
冶金工业 | 7106篇 |
原子能技术 | 2673篇 |
自动化技术 | 27372篇 |
出版年
2025年 | 222篇 |
2024年 | 3021篇 |
2023年 | 3051篇 |
2022年 | 4905篇 |
2021年 | 5673篇 |
2020年 | 6055篇 |
2019年 | 5119篇 |
2018年 | 4873篇 |
2017年 | 5770篇 |
2016年 | 7044篇 |
2015年 | 7195篇 |
2014年 | 11481篇 |
2013年 | 11574篇 |
2012年 | 13460篇 |
2011年 | 14451篇 |
2010年 | 10393篇 |
2009年 | 10556篇 |
2008年 | 9912篇 |
2007年 | 11844篇 |
2006年 | 10300篇 |
2005年 | 8672篇 |
2004年 | 7323篇 |
2003年 | 6236篇 |
2002年 | 5057篇 |
2001年 | 4158篇 |
2000年 | 3552篇 |
1999年 | 2967篇 |
1998年 | 2548篇 |
1997年 | 2144篇 |
1996年 | 1764篇 |
1995年 | 1464篇 |
1994年 | 1313篇 |
1993年 | 982篇 |
1992年 | 906篇 |
1991年 | 661篇 |
1990年 | 562篇 |
1989年 | 473篇 |
1988年 | 401篇 |
1987年 | 269篇 |
1986年 | 235篇 |
1985年 | 215篇 |
1984年 | 252篇 |
1983年 | 239篇 |
1982年 | 196篇 |
1981年 | 96篇 |
1980年 | 96篇 |
1979年 | 65篇 |
1978年 | 53篇 |
1977年 | 46篇 |
1976年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
This paper introduces a high precision 7m laser measuring instrument developedby the anthors and its operating principle,and systematically analyses the errors havinginfluence on the performance of the measuring instrument.Error analysis and actualverification indicate that all the characteristics reached or exceeded the original designspecifications. 相似文献
142.
采用基于特征的多面体造型方法,解决了压力容器壳体曲面造型的问题,同时,提出了一种筒体展开的算法,并进行了误差分析与修正。 相似文献
143.
混凝土构件火灾后损伤程度鉴定和加固 总被引:3,自引:0,他引:3
王秀逸 《西安建筑科技大学学报(自然科学版)》1997,(4)
通过实际工程的调查和对砼材料在不同受火情况的试验研究,论证了采用外部特征综合分析并配合回弹试验等是判断砼构件火损程度的简便而实用的方法。 相似文献
144.
Robust Estimation of Rotation Angles from Image Sequences Using the Annealing M-Estimator 总被引:1,自引:0,他引:1
A robust method is presented for computing rotation angles of image sequences from a set of corresponding points containing outliers. Assuming known rotation axis, a least-squares (LS) solution are derived to compute the rotation angle from a clean data set of point correspondences. Since clean data is not guaranteed, we introduce a robust solution, based on the M-estimator, to deal with outliers. Then we present an enhanced robust algorithm, called the annealing M-estimator (AM-estimator), for reliable robust estimation. The AM-estimator has several attractive advantages over the traditional M-estimator: By definition, the AM-estimator involves neither scale estimator nor free parameters and hence avoids instabilities therein. Algorithmically, it uses a deterministic annealing technique to approximate the global solution regardless of the initialization. Experimental results are presented to compare the performance of the LS, M- and AM-estimators for the angle estimation. Experiments show that in the presence of outliers, the M-estimator outperforms the LS estimator and the AM-estimator outperforms the M-estimator. 相似文献
145.
本文从热电厂的盈亏分析入手,找出了最佳的盈亏平衡点,从而给出热价函数和电价函数,在一定程度上解决了热价制定难的问题。 相似文献
146.
采用了电缆材料绿色化的两大指标———毒性和有害元素含量的两种检测方法,即细胞毒性试验和电感耦合等离子体发射光谱仪法,认为这两种方法具有简便、精确、快速和省钱等优点,文中也提供了某电缆阻水膏和某种电缆护套料分别进行毒性试验和有害元素检测和分析。 相似文献
147.
148.
A contribution to the development of strategic control and planning instruments: An acquisition case study 总被引:1,自引:0,他引:1
A. Chevalier P. L. Kunsch J. P. Brans 《International Transactions in Operational Research》2004,11(2):155-168
The present paper is part of the efforts made by the authors in recent years to develop strategic control and planning instruments in corporations using OR‐techniques like system dynamics, control theory, and group multicriteria decision aid. A more general framework called ‘adaptive control methodology’ (ACM) combines all these techniques. It has been presented in several papers. The objective of the present analysis is to calibrate this instrument and to tune it to the corporate needs by analysing real‐world applications. More specifically, several case studies have been investigated in large multinational organisations in the food sector. An acquisition case has been used for the calibration purpose. It is analysed in the paper from the ACM perspective to provide additional material for revisiting and improving the methodology. 相似文献
149.
Extrapolating technology advances in the near future, a computer architecture capable of petaflops performance will likely be based on a collection of processing nodes interconnected by a high-performance network. One possible organization would consist of thousands of inexpensive, low-power symmetric multiprocessor (SMP) nodes. Each node will inject data into the interconnection network at a very large rate and consequently, the interconnect scheme is one of the most crucial design issues affecting system performance. This paper describes the 2D simultaneous optical multiprocessor exchange bus (2D SOME-Bus) which has the potential to become the basis of a high-end computer architecture capable of petaflops performance. It consists of N horizontal, N vertical 1D SOME-Bus networks, and N
2 nodes. Each node is connected to one horizontal and one vertical 1D SOME-Bus. Each of N nodes connected to one 1D SOME-Bus has a dedicated broadcast channel and an input channel interface based on an array of N receivers monitoring all N channels and allowing multiple simultaneous broadcasts. In the 2D SOME-Bus, messages being broadcast on one Bus can be broadcast in a cut-through manner on one or more Buses in the other dimension. This paper describes the optoelectronic devices and technology which make the 2D SOME-Bus possible, and the network interface organization. It also presents simulation results which compare the performance of the 2D SOME-Bus, the 1D SOME-Bus, the crossbar and the torus under the message-passing paradigm. 相似文献
150.
Perturbation Analysis of Multiclass Stochastic Fluid Models 总被引:1,自引:5,他引:1
Gang Sun Christos G. Cassandras Christos G. Panayiotou 《Discrete Event Dynamic Systems》2004,14(3):267-307
We use a stochastic fluid model (SFM) to capture the operation of finite-capacity queueing systems with multiple customer classes. We derive gradient estimators for class-dependent loss and workload related performance metrics with respect to any one of several threshold parameters used for buffer control. These estimators are shown to be unbiased and directly observable from a sample path without any knowledge of underlying stochastic characteristics of the traffic processes. This renders them computable in on-line environments and easily implementable in settings such as communication networks. 相似文献